1. Field of the Invention
The invention relates to a stackable screen module arrangement for use in a stacked vibratory screen assembly. The invention also relates to such a stacked vibratory screen assembly.
2. Description of Prior Art
Known in the prior art are vibratory screens for, for example screening material such as gravel, crushed rock and the like. Examples of such vibratory screens are illustrated in, for example, U.S. Pat. No. 3,285,413, Taylor-Smith, Nov. 15, 1966, U.S. Pat. No. 3,341,012, Thacher, Sep. 12, 1967 and U.S. Pat. No. 4,340,469, Archer, Jul. 20, 1982.
The '413 patent teaches a stacked screen arrangement including overlapping screens 35 and 36. As can be seen, the '413 patent does not teach a module such arrangement.
The '012 patent teaches an arrangement including a plurality of stacked screens 190 having side walls 198. (See FIG. 2). The adjacent screens are rods 201 and 203 fastened at their lower ends 206 and 208 to opposite sides of a base plate 125 of the screen unit 15, as is illustrated in FIG. 2 of the '012 patent. Although the screens and side walls 198 could be seen as forming modules, the hold down and clamping means is a relatively awkward arrangement, and there is no real explanation in the '012 patent about how the spacers between side walls 198 are held in place.
The '469 patent also teaches a stacked screen arrangement. As seen in FIG. 1 of the patent, screens 22, 23 and 24 are stacked in a vertical direction and held in frame 15 which includes side walls 16 and 17. As can be seen, each side plate 16 and 17 is a one-piece construction. Such large side plates are difficult to handle, and separate type plates must be provided for horizontal versus inclined screen arrangements. There is no teaching in the '469 patent relating to the possibility of modular constructions.
In addition, with the '413 and '469 patents, as the vibrators have to be formed on the site, they cannot be pre-assembled, nor can the vibrators be shipped as units.
Further difficulties with the '413 and '469 arrangements are that the vibrators have to be formed on the site as they are formed within the assembled frames. As there is a good deal of dust and sand on the sites, the vibrators can be contaminated during the formation thereof. Additionally, the sites are not the most convenient places for assembling the vibrators.